Design Integration Laboratory

Architecture 222, 410/510, and 610

Project Notes -- Scaling a Drawing for Measuring

Objective

These notes are intended to help set up drawings for use in making a measured drawing or model. It describes a process for converting a drawing at a strange scale to a standard scale for easy measurement of drawing elements.

Starting Point

We will assume you are starting out with a drawing at a non-standard scale. You'll need to know the dimension of part of this drawing to perform the scale conversion. This dimensional knowledge can be in one of two forms: 1) an accurate clear overall dimension of the actual building, 2) a element of known size, either a graphic scale which is part of the drawing, or with a little more difficulty, any other drawing element of known size, possibly estimated.

Basic Measurement

1. If you have an actual measurement of some obvious overall dimension of the building available, you can proceed directly to the next step, Establishing Scaling Factor.

2. If the drawing has a graphic scale, or shows any other element for which you can accurately determine a real-world size, then figure out the overall length it represents in real-world units. Let's call this length LGr (for Length, Graphic scale, real).

   Then measure the graphic scale in any convenient temporary units - millimeters, pixels, 1/16ths of an inch, or whatever. Let's call this length LGt (for Length, Graphic scale, temporary units). The accuracy of this measurement is critical to the overall calculation.

   Using the same temporary units, whatever you chose, carefully measure some obvious dimension of the building in the drawing. Let's call this length LBt (for Length, Building, temporary units).

   Now you can calculate the number you really want, which is LBr, for Length, Building, in real units:

   LBr = LBt * (LGr/LGt)

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Establishing Scaling Factor

Once you know some obvious overall real dimension for the building shown in your drawing, you can calculate the scaling factor to use to adjust the drawing to an even scale.
1. Decide on the scale you want the drawing to end up at. Get out an architectural scale which measures in the scale you want to get to.

2. Measure the known overall dimension of the building in the original drawing, using the scale you want to end up with. We'll call this measurement LOs (for Length, Original, in scale units). If I want to scale the drawing shown above to 1/8" = 1'-0" scale, I'll measure the known height in 1/8ths of an inch, getting LOs= 7 feet.

3. We know this dimension should actually equal LBr, the real building dimension, in the scale units, when we're done. The scaling factor, SF, to get there is SF = LBr / LOs. In our example, SF = 15/7 = 2.14, or for a copier, 214%.

4. Scale the original drawing by this factor, in software or using a copier. Then check your key measurement with the proper scale, to make sure the steps have all come together correctly.